ESTRO 38 Abstract book

S921 ESTRO 38

Research Center DKFZ, Radiology, Heidelberg, Germany ; 5 National Center for Tumor Diseases NCT, Partner Site Heidelberg, Heidelberg, Germany ; 6 National Center for Radiation Research in Oncology, OncoRay, Dresden, Germany ; 7 Institute of Radiooncology – OncoRay, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany ; 8 German Cancer Consortium DKTK, Partner Site Dresden, Dresden, Germany ; 9 National Center for Tumor Diseases NCT, Partner Site Dresden, Dresden, Germany ; 10 Technische Universität Dresden, Department for Radiotherapy and Radiation Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus, Dresden, Germany ; 11 University Hospital Heidelberg, Radiation Oncology, Heidelberg, Germany Purpose or Objective Radiotherapy needs anthropomorphic multimodality phantoms to simulate the treatment of cancer. In this work, we address two requirements and focus on the simulation of prostate cancer treatment: (i) A PSMA- PET/MRI based treatment planning should be simulated and for the following irradiation (ii) the phantom should be able to perform 3D dose measurement by using polymer gels (PG). We present a modified version of the ADAM- pelvis phantom [1] (Anthropomorphic, Deformable And Multimodal), the ADAM with PET extension (ADAM PETer). [1] Niebuhr et al. Med Phys 43(2), pp.908-16, 2016, Technical Note: Radiological properties of tissue surrogates used in a multimodality deformable pelvic phantom for MR-guided radiotherapy. Material and Methods The same basic data as ADAM's is used for the rework of the construction. New possibilities in the 3D- printing made it possible to redesign the shape of the bone in more detail by using the software Geomagic® Freeform®. Now more details of the pelvis bone and all the parts of the joint are visible. For all other modifications, the software Autodesk inventor® was used. Bone tumors and the lymphatic system were integrated. The prostate was modified in such manner that subdivisions or internal spheres (tumor simulation) were created and filling operations from the outside of the segment are now possible. All parts of the phantom are printed by means of a 3D- printer (Stratasys, Objet 300 Connex 3) from the material VeroClear TM and Agilus30 TM . Only the bladder, the muscle and adipose tissue are produced like in ADAM. For PSMA-PET/MRI based treatment planning, gels of different agarose concentrations were mixed with gadolinium and radioactive tracers are added in variant 2 (fig 1b), in the lymphatic system (fig. 1c) and in the bone tumors (fig.1c). In a first irradiation experiment, the prostate variant 1 (fig. 1a) filled with PG was set as target and homogenously irradiated.

Results The new version of ADAM, in which a bone tumor, the lymphatic system and prostates of different types were included, was produced in a 3D-printing process. It is now possible to insert two bone tumors from outside the phantom. Thus, a simpler handling with radioactivity is facilitated. Further possibilities for tumor simulations with radiotracers are offered by the design of the lymphatic system and the prostate. Both are a closed system in the phantom, such that radiotracers are confined to within these structures. An anthropomorphic multimodality phantom of the pelvis was created with modular prostate design in which, depending on the configuration, either gel dosimetry can be performed or patient-like PSMA-PET/MR data for treatment planning can be generated. Conclusion With the revised ADAM-pelvis phantom, it was possible to extend the possibilities in simulating end-to-end in radiation therapy. This includes the use of radioactive tracers for treatment planning and the insertion of PG for dose verification in 3D. EP-1711 Discover Prostate SBRT or Validation of motion-tracked SBRT treatments with a transmission detector M. Szegedi 1 , A. Paxton 1 , V. Sarkar 1 , P. Rassiah 1 , H. Zhao 1 , G. Nelson 1 , F. Su 1 , J. Huang 1 , J. Kunz 1 , D. Spitznagel 1 , B. Salter 1 1 University of Utah Huntsman Cancer Hospital, Radiation Oncology- Medical Physics, Salt Lake City, USA Purpose or Objective IMRT treatments are typically validated prior to delivery to a patient. There is an assumption that after this initial validation, the patient treatments are delivered correctly. This work reports the patient treatment validation results during ultrasound (US)-image guided and tracked prostate SBRT treatments using a collimator-mounted diode transmission (CM DT) detector. Material and Methods A recently introduced Delta 4 Discover (ScandiDOS) CM DT detector was commissioned for clinical use. Used as